Grading system with electrical contact



July 17, 1962 D. E. ATKINSON 3,044,195

GRADING SYSTEM WITH ELECTRICAL CONTACT Filed June 20, 1960 2 Sheets-Sheet 1 INVENTOR DUANE E. ATKINSON ATTORNEY July 17, 1962 D. E. ATKINSON 3,044,195

GRADING SYSTEM WITH ELECTRICAL CONTACT Filed Jun'e 20, 1960 2 Sheets-Sheet 2 52b 2 X420 r 440 39a 52a =A46 42D INVENTOR DUANE E. ATKINSON BY f%W/ ATTORNEY FIG. 4

United States Patent 3,044,195 GRADING SYSTEM WITH ELECTRICAL CONTACT Duane E. Atkinson, 102 Fey Drive, Burlingame, Calif. Filed June 20, 1960, Ser. No. 37,369 9 Claims. (Cl. 37-143) This invention relates generally to vehicle control systems and more particularly to such systems which are guided by an electrical contact.

In leveling a road bed in preparation for paving, it is necessary that the grading be even and accurate. It is well known that specifications for the paving of road beds is determined from several factors, among which is the finished elevation of the paved road and the thickness of the paving. Consequently, the road bed must be below the desired finished road surface at least a distance equal to the specified thickness of the paving.

In addition, it is realized that in the actual construction of the paved road, large amounts of material are employed. If the final road bed has been prepared deeper than is required by the specification, the additional thickness of the paving material to bring the road elevation up to the required elevation creates a large additional expense on the contractor.

By present methods, the road bed is roughly graded by bulldozers or other such equipment to the preliminary level. Subsequently, a line is stretched and suspended along the road bed by surveyors. The line not only indicates the general horizontal location of the road but indicates, in addition, the actual level of the desired road surface. Using the line as a guide, the road bed is again graded keeping a predetermined distance below the line which is stretched. This operation may include digging a trench along the line with subsequent laying of rails or it may include overall grading of the entire road surface. When the rail trench alone is dug, the rails are laid and serve as a guide for leveling the remainder of the road surface.

At present, this finished leveling either of the rail trench or of the entire bed is accomplished by the operator of the-final grading vehicle observing the line and visually keeping the proper position of the cutting blade.

More recently advances have been made in the art wherein road leveling may be accomplished in an automatic or semi-automatic operation. In some of these operations, levers are disposed about the stretched line and serve to contact the line and mechanically activate a switch for adjusting the blade. Although such a system is definitely an advance in the art of road leveling, it has several disadvantages. The flexing of the stretched line is inherent in applying force to throw the switch as is the actual movement of the arm in order to activate the switch. Each of these deficiencies causes an error in the position of the blade.

Such errors, although small in themselves, create considerable expense on the contractor due to the large amount of materials involved in laying the paved road. Other automatic and semi-automatic systems which have been devised include pendulums, gyroscopes, depth pressure gauges, visual level indications, and mercury switches. Each of these has had little success due to their fragile nature, expense or reliance on human judgment.

Moreover, in the leveling of other surfaces such as beds for pipelines and drainage ditches, an accurate finished surface is desirable.

It is, therefore, an object of this invention to provide an improved vehicle control system.

It is a more particular object of this invention to provide an improved vehicle control system wherein a stretched electrically conductive line, indicative of the finished surface, is utilized as a conductor; and sensing means disposed on grading equipment adjacent the line serve as a sensing electrical pickup from the line for guiding the grading blade.

It is another object of this invention to provide a grading system of the aforementioned character wherein the sensing means serves to adjust the blade.

It is still another object of this invention to provide a grading system of the aforementioned character wherein the sensing means not only controls blade adjustment but also the actual steering of the vehicle.

These and other objects of the invention will become more clearly apparent upon reading the following description in conjunction with the accompanying drawing.

Referring to the drawing:

FIGURE 1 is a perspective view of a grading vehicle in operation in accordance with the present invention;

FIGURE 2 is an enlarged view of a portion of FIG- URE 1 showing the novel contact apparatus in accordance with the invention;

FIGURE 3 is a schematic block diagram of an electrical circuit as used in accordance with one embodiment of the invention;

FIGURE 4 is a schematic block diagram of an electrical circuit as used in accordance with another embodiment of the invention;

FIGURE 5 is a schematic diagram of still another embodiment of the invention wherein a radiator is utilized to electrically activate the line; and

FIGURE 6 is a schematic diagram of another embodiment of the invention wherein the invention is used to steer a vehicle.

Referring to FIGURE 1, a line 11 is shown stretched between the posts 13 and grounded. A grading tractor 19 is shown in operation adjacent to the line 11 in the road bed 21. The tractor includes a cutting blade 23 and a final leveling blade 25, which are in fixed relationship with each other to operate at the same level. Pickups 27 and 29 are disposed above and below the line 11, respectively. These pickups are afiixed to but insulated from the blade, and serve to provide an electrical signal for blade adjustment in a manner to be described hereinafter.

FIGURE 2 shows a more detailed view of the pickup arrangement. Itis seen that in addition to the pickups 27 and 29, there are also pickups 31 and 33. The pickups 31 and 33 are disposed approximately at right angles to the pickups 27 and 29 and all of the pickups are pivoted about a pivot shaft 35. The upper pickups 27 and 31 are connected together electrically. Likewise, the lower pickups 29 and 33 are connected together electrically.

All of the pickups 27, 29, 31 and 33 are spring urged in a clockwise direction about the pivot shaft 35 as shown in FIGURE 2. A stop is employed in conjunction with the spring such that the pickups 27 and 29, in their normal position, are disposed approximately perpendicular to the line 11. As the tractor moves from right to left as viewed in FIGURE 2, the pickups 27 and and 29 disposed above the below the line 11 may come in contact with one of the upright posts 13. Upon such contact the pickups 27 and 29 are urged against the spring force in a counter-clockwise direction and rotated about the pivot 35. With this rotation, the pickups 31 and 33'become disposed above and below the line 11 on the left hand side of the posts 13. After pickups 27 and 29 pass the post 13, the spring force about the pivot 35 causes the pickups 27 and 29 to again be disposed above and below the line 11, respectively. The pickups 31 and 33 are again disposed approximately parallel to the line 11.

The vertical spacing between the pickups 27 and 29, and likewise between the pickups 31 and 33, need only to be slightly greater than the thickness of the line 11. Since the system works on an electrical contact principle, it is unnecessary to apply pressure to the line 11 or to s earer) the pickups 27 and 29. Merecontact is required between one of the pickups 27 or 29 with the line 11 and deflection of the line or the pickups themselves is not necessary and is preferably minimized. Thus, it is seen that there is relatively little play orerror in the system.

Referring to FIGURE 3, a schematic circuit diagam of an electrical circuit employed in one embodiment of the invention is shown. The pickups 27 and 31 are shown above the line 11 and the pickups 29 and 33 are shown below the line 11. Associated with each pair of contacts is a high voltage source, 35a and 35b respectively. Since the circuits associated with each of the pairs of contacts are identical, only the circuit associated with the upper contact assembly will be described in detail, it being realized that the other circuit is identical.

The pickups 27 and 31 are connected to the voltage source 350 through a current limiting resistor 37a. The other terminals of the high voltage source are connected to the base of the transistor 38a as an emitter follower. The output across the resistor 39a is applied to the base of the transistor 4% which is connected as a power amplifier to apply power from the battery 41 to the solenoid 42a. A stabilizing resistor 44a is provided which is connected between the base of the transistor 38a and ground. A grounding means 46 grounds one terminal of the resistor 39a and of solenoid 42a. The grounding means may, for example, be a probe, plow, drag or steel wheels on the equipment. The circuit between the line 11 and the grounding means 46 includes the resistance offered by the ground, schematically illustrated by resistor 47.

When the probes 27 or 31 are in contact with the line 11, current will flow through the loop including the ground resistance 47, power source 35a, and associated electrical circuit. The current will be amplified by the emitter follower including the transistor 38a and will serve to turn on the power transistor a to apply battery voltage to the solenoid 4.2a.

Thus, it is seen that when the blade carrying the pickups is lower than it should be, the pickups 27 or 31 contact the line 11 and complete the circuit. This causes operation of the solenoid 42a. The solenoid may control the application of power to a motive means which controls the blade position. The converse is likewise seen if the blade carrying the pickups is higher than the desired voltage. The lower pickups 29 or 33 will contact the line 11 and the electrical circuit including the elements carrying the subscript b will be activated to cause the system to lower the blade.

FIGURE 4 shows another embodiment of the invention. The embodiment is similar to that shown in FIG- URE 3 and like reference numerals are applied. The essential differences are the inclusion of A.-C. power sources 51a and 51b in place of the D.-C. power sources 35a and 35b. Diodes 52a and 52b are provided to rectify the signal current for application to the amplifier which includes the emitter follower stage and power stage. The amplifier operates as previously described to activate, through earth, either one or the other of the solenoids which, in turn, control the blade position.

This latter embodiment has an advantage over the embodiment shown in FIGURE 3 in that A.-C. signals provide easier pickup than D.-C. pulses. The A.-'C. signals are not so much impeded by deterioration of the line such as by rust or oxidation. In addition, the A.-C. which might be high frequency is easy to ground. Capacitive coupling between the equipment frame and earth aids grounding, even with poor resistive coupling. The use of A.-C. permits lower voltages, and consequently reduces the danger to personnel using the system.

As a variation in the use of the A.-C. system, the grounding rods 17 may be eliminated and signal source applied to the line 11 by use of a radiator 57 located on the tractor and positioned adjacent the line 11 as shown in FIGURE 5; In such a manner, the circuit loop would include the A.-C. sources 51a and 51b, the amplifiers,

A the radiator 57, the line 13., and the pickups 27, 29, 31 or 33-. The operation of the system would be identical with the exception that the circuit values would have to be adjusted to accommodate the elimination of the ground resistance 47.

With the employment of a larger leveler than the trench digger shown in the figures, such as a bulldozer having a relatively wide blade, it would be convenient to mount one of the sensing circuits on each side of the blade with a lead line stretched on both sides of the bulldozer path. Thus, not only the elevation of the blade but the angle of inclination could be simultaneousy adjusted.

It is seen, therefore, that a new and improved vehice control system is provided wherein a minimum of contact between the pickup and the lead line is necessary. Consequently, deflection of the lead line and of the pickups themselves is held to a minimum and the blade position is extremely accurate.

Moreover, it is apparent that the control system described may be utilized not only for levelling road beds but for grading any surface where a grading vehicle is used in conjunction with an adjustable blade. Other such uses would include trench digging such as for drainage ditches, pipeline beds, or cuts for poured foundations.

it is also apparent that the control system described may be utilized not only for vertical adjustment of a blade but may likewise be extended to steering of the vehicle itself as shown in FIGURE 6. In such a system, pickups 61 similar to those described may be arranged in a vertical plane above the lead line 11 to provide steering.

I claim:

1. A vehicle control system for controlling grading apparatus of the type which is adapted to establish a graded surface comprising a lead line disposed a predetermined elevation above the surface to be graded, said ead line being electrically conductive and grounded to earth, circuit loop means including said lead line and earth, means on said vehicle and coupled to said circuit loop for energizing said circuit loop means with electrical energy, the means for energizing the circuit loop being grounded to earth, means in said circuit loop cooperating with said lead line and serving to derive a control signal, and means responsive to said control signal serving to control the grading apparatus whereby it establishes a grade which is a predetermined level below the lead line.

2. A vehicle control system as defined in claim 1 wherein said means for producing the electrical signal is a direct current source.

3. A vehicle control system as defined in claim 1 wherein said means for producing an electrical signal is an alternating current source.

4. A vehicle control system as defined in claim 1 wherein said circuit loop includes an electrical pickup affixed to said blade.

5. A system as defined in claim 4 wherein two said circuit loops are included, one of said loops being operable to adjust said blade in one direction and the other said loop being operable to adjust said blade in the other direction.

6. A system as defined in claim 5 wherein each of said pickup loops includes an electrically conductive arm, one said arm being disposed above said lead line and one of said arms being disposed below said lead line.

7. A vehicle control system as defined in claim 4 wherein said electrical pickup comprises a first pair of arms and a second pair of arms displaced from said first pair by an approximate right angle, said line adapted to be disposed between said first pair of arms, both of said pairs being resiliently urged about a vertical pivot shaft, a stop associated with said arms wherein said first pair maintains a home position approximately perpendicular to said line and upon contact with an obstruction said arms rotate about said pivot shaft wherein said line becomes disposed between said second pair of same.

8. A vehicle control system as defined in claim 1 together with means for steering the vehicle responsive to a second electrical signal, means disposed adjacent said lead line in a vertical plane for deriving said second electrical signal, and circuit loop means including said lead line for delivering said second signal to the means for steering the vehicle.

9. A-vehicle control system for controlling grading ap-- paratus of the type which is adapted to establish a graded surface comprising a lead line disposed a predetermined elevation above the surface to be graded, said lead line being electrically conductive, an electromagnetic radiator in close proximity with said lead line, a pick up arm aflixed to the grading apparatus, said pick up arm having contact means for continuing said lead line, circuit loop means including said radiator, said lead line and one of said contact means when in contact with the lead line, means coupled to said circuit loop for energizing said circuit loop means with electrical energy, means in said circuit loop cooperating with said lead line and serving to receive a control signal, and means responsive to said control sig nal serving to control the grading apparatus whereby it establishes a grade which is a predetermined level below the lead line.

References Cited in the file of this patent UNITED STATES PATENTS 1,980,553 Salisbury Nov. 13, 1934 2,509,914 Goodwine May 30, 1950 2,873,541 Eliason Feb. 17, 1959' 2,947,097 Toews Aug. 2, 1960 

